Recovery of unfermentable residues



Dec. 17, 1940. I CHHSTENSEN 2,225,428

RECOVERY OF UIQIFERMENTABLE RESIDUES Filed Jfily 26, less Patented Dec. 17, 1940 UNITED "STATES 2,225,428 RECOVERY OF UNFERMENTABLE RESIDUES Leo M. Christensen, Atchison, Kans 'assignor 'to The Chemical Foundation, Incorporated,a corporation of Delaware Application July 26, 1938, Serial No. 221,453

11 Claims.

This invention relates to a method of economically recovering unfermentable residues, more particularly to a process of treating distillery slop to produce an improved food product therefrom.

The production of alcohol from grains, as is known, involves essentially the saccharification of the starch in the grain to fermentable sugars and the fermentation of such sugars to alcohol 1" and carbon dioxide. Since such reactions involve substantially only the starch content of the original grain, there remains, as a residue, all the protein's, crude fiber, minerals and oil of the original raw material. From the standpoint of a d feed for live stock, these unfermentable constitucuts are the most valuable part oi the grain. In addition to the nutritious constituents of the original grain, there is also present in the dealcoholized slop a considerable amount of yeast which is formed during the fermentation step.

The amount of these residues is quite considerable. Thus, when a bushel of corn is treated to produce alcohol, there remains from substantially 16 to 18 pounds of unfermented residues, which quantity comprises substantially 25 to per cent.

(dry basis) of the original grain which was processed.

The valueof such a feed has long been recognized and many methods of recovering it have 30 been proposed. The product finds a ready market and, at the present time, the entire production is insufiicient to meet the demand.

Under the present process an improved type of feed, in a novel physical state '(distillers dried grain), may be produced. This product has a very high percentage of protein, usually not less than 28%, which protein content is practically 90% available. The improved product is a peculiarly advantageous feed for dairy cows, since [0 it is as complete as milk casein in its content of amino acids.

The recovery of these distillers grains in such a manner as to retain the full dietetic value of the constituents presents many problems. The crude beer slop contains on the average about 7% of total solids, about one-half of which are in the form of relatively large suspended particles, andthe other half in the form of very fine and highly dispersed suspensoids and colloids, and

0 some soluble constituents. The recovery of these valuable constituents necessitates the handling and separation of very large quantities of water.

It has been proposed in the past to treat dis-- 5 tillers slop by passing the slop in hot condition over screens so as to separate out the larger and readily filterable particles. The separated wet solids were then further dewatered, as in a press, and were treated in a rotary steam or direct fire heated drier. The filtrate or thin slop 5 from the first screening operation was treated in various manners, suchfor example as in a multiple efl'ect evaporator, so as to concentrate the solution to a syrup. It has been proposed in the past to produce a separate feed from this syrup 10 and also to add the syrup to the larger filtered grains passing to the rotary drier. a

The treatment of the finer protein materialy' that is to say, that occurring in the so-called soluble. form, in the past has been attended 15 with considerable difliculty. This material is of a colloidal nature and tends to form syrupy or gelatinous systems of high viscosity when in fairly highly concentrated form. Thus in the past when ithas been attempted to dry such syrup down in a rotary drier, the material tends to stick to the sides of the drum. Furthermore, in the past it has been extremely diflicult homogeneously to incorporate the concentrated protein syrup inthe preliminarily separated solids. Such 2g syrup, as noted above, is a liquid of relatively low fluidity and thus tends to coat the surfaces of the larger particles separated out on the screen. In these circumstances the protein syrup penetrates the larger particles to only a minor degree and uniform drying of the mixed product is therefore extremely difiicult. t

It has now been found that the valuable nutritious constituents of the original raw material may besubstantially quantitatively recovered and in the form of a novel and improved product. A characteristic feature of the invention is the fact' that the larger particles of the distillers slop are first separated out from the slop, as by screening, are then dried down to a certain 40 definite optimum moisturecontent/and are subsequently contacted with a protein solution of selected optimum concentration under such circumstances that the concentrated solution readily penetrates the preliminarily dried particles, so as homogeneously to be distributed therethrough. This mixed product is then subjected to a special type of flash drying whereby the product is dried down to the desirable extent and under such controlled conditions of temperature and time that caramelization and/or decomposition of the protein constituents is avoided. As will be seen more fully hereinaftenthe major advantages of the invention may be attained by subjecting the larger solid particles or aggregates of the slop to a preliminary drying under controlled conditions of temperature-such that this material is rendered absorptive to the relatively viscous concentrated special type of flash drying whereby the moisture content is reduced to the desired extent and in the minimum' time. In these circumstances, as will appear more fully. the thoroughly saturated particles are extenuated or dispersed through the hot gas phase and the individual particles are quickly and uniformly dried down in a minimum time, thus avoiding prolonged contact with high temperature gases and corresponding thermal decomposition. It will be appreciated that this type of treatment insures the production-of a product of improved physical characteristics. The feed, produced under this method of homogeneous impregnation of the fibers by the concentrated protein solution, followed by thespecial flash drying, is of a characteristic light brown color which sharply distinguishes it from the darker products produced by complete drying in rotary driers. The new product similarly is of a light flufly nature, the individual particles of which are crisp and frangible. This p ical state is due in part to the fact that the finer protein solids, originally contained in the thin slop,'in-

stead of being present on the surface as a type of mucilaginous coating, are distributed through the interstices of the fibrous particles themselves, and in part to the fact that, in sharp contradistinction to older methods, the impregnated solids are not-tumbled or modulated ina rotary element like the rotary drier.

It will be observed-that the present method invokes several advantageously correlated concepts, the utilization oi which insures a particularly effective drying with the production of an improved product. These broader concepts o include the preliminarily controlled drying of 60 screened solids, when thus specially preconditioned, are then not merely wetted by the syrup,

but are actually impregnated or saturated with the syrup. To insure such optimum impregnation, as will appear more fully, the conditions as of syrup concentration are carefully controlled such that the syrup produced in the new method is of optimum penetrability with respect to the preconditioned screened solids. It might well be observed at this point that, in the present 70 process, the concentration of the syrup is not carried out to'the maximum extent, i. e.. to secure a. very high protein concentration, but is controlled short of this point for the purposes stated. The saturated, preconditioned screenings are then extenuated or highly dispersed in a gaseous medium and are flash dried with hot gases. After such fiash drying, or rapid removal of moisture from all surfaces or the particles,

' the temperature of the product is rapidly reduced to avoid charring and proteolytic decomposition.

It will be appreciated that a process, embodying the several concepts expressed above, may be carried out in a number of specifically diti'erent forms of apparatus and with modified types of flow circuits of the screenings, syrup and drying medium, respectively. To more completely explain the invention, a preferred form of apparatus is shown in the accompanying drawing, it being understood that this is given as illustrative and not as the exclusive means available for employment under the invention.

In the single figure of the accompanying drawing is indicated, diagrammatically, a preferred arrangement of units which has been found to be effective. While not shown, it is to be understood that this apparatus is associated with a still house, the slop from the beer still of which is to be treated according to the invention.

The major stages of the process comprise a screening stage, indicated generally by the letter A, in which the crude slop, containing on the average about 7% 01' solids, is filtered or screened to separate the wet solids from the thin filtrate or slop; a preconditioning-drying stage, indicated generally by the letter B, in which the screenings from stage A, and which contain about 70% of moisture, are dried down to a definite moisture content; a concentration stage C, indicated on the drawing as a quadruple eiiect evaporator in which the filtrate or thin slop is concentrated down too. definite concentration of solids; an impregnating stage D, indicated on the drawing as a mingler, in which the preconditioned screened solids are impregnated with the concentrated protein solution; a drying stage E,in which the impregnated preconditioned solids are dried down under definite conditions of temperature control so as to produce a light, flocculent, dried feed; and a final stage, I", indicated as a hopper structure in which the dried solids are weighed and bagged.

Each of these stages may be modified considerably as to structure and design, while fulfilling the major functions demanded according to the present invention.

Considering the apparatus and the fiow oi material in more detail, the beer slop is withdrawn from the beer still or from a storage receptacle by a pump (not shown) and is conveyed through line I to the dry house unit. The beer slops are discharged from line I- into the screening stage series'of press rolls l,'driven through any suit-' abletmechanismbythemotor'l. In this device the screenings discharged from screens 2 and 3 are subiected to mechanical pressure to express additional amounts or soluemployed for this stage.

tion therefrom. The liquid which is expressed from the screenings accumulates in a suitable the trough 2B and is passed thence either under a gravity head or pump pressure through the line 2| to the thin slop storage tank 22. From this tank the slop is picked up by pump 23 and passed, in amounts controlled by valve 24, through the line 2 5 to a suitable concentration stage and preferably to the quadruple effect evaporator 26 as shown. The steam-lines and other connections of the quadruple effect evaporator, for the sake of simplicity, have been omitted but it being understood that any suitable type of multiple effect evaporator may be Connected to the last effect is the barometric condenser unit 21 which, similarly, may be of any suitable construction and preferably, as shown, comprises a multiple jet barometric condenser. The concentrated slop or syrup is withdrawn from the last effect through the line 30 and is forced by pump 3| through the lines 32 and 33 to the syrup tank 34, and whence it may be passed, in a manner to be described, to an impregnation stage in which it is utilized to thoroughly saturate the preconditioned screened solids.

Where circumstances so require, as for example when the unit is shut down. syrup accumulating in the last effect may be by-passed through line 83' to the storage tank 22.

The solid material separated out by the screens and which has been preconditioned in the stage B is picked up by the exhaust fan 40 and is forced upwardly through the line 4| to the rotary drier cyclone 42. This. cyclone is provided with the flue gas exhaust vent 43 which may discharge to the atmosphere or may be connected to any suitable absorption unit for the recovery of valuable components of the flue gases.

The hot, partially dried screenings pass downwardly through the cyclone 42 to the hopper 44, where they are sprayed or otherwise intimately contacted with the protein syrup or concentrate. To facilitate impregnation of the screenings by the syrup, such syrup is preferably heated to an elevated temperature by means of steam coil 45 and is forced, under pressure, by means of the pump 46, into the hopper 44. The flow of the syrup may be controlled by means of regulating valve 41. While, as indicated, it is preferred to heat the syrup and force it under positive pressure, it is clearly to be understood that the heating means 45 may be dispensed with and gravity flow of the syrup utilized.

After being wetted by the syrup, the solids are tumbled in the mingler 48. This mingler is provided with the screw conveyor 49 which serves to convey the material from the hopper to the flash drier. While the screenings are moved through the mingler, they are continuously agitated to insure complete wetting of the screened particles by the solution and are insured an adequate length of time or travel so as to permit thorough impregnation by the syrup. .The impregnated screenings are then discharged from the mingler to a rotary feedingmechanism 50 in which the screenings are dispersed or broken up to prevent agglomeration and clogging of the unit. It has been found advisable to insert an air damper 5|, opened to a suflicient degree, in the line between the rotary feeder and the flash drier. In these circumstances, due .to the flow of gases through the unit, a flow of air through the damper 5| is induced into the feed line which serves most eflectively to prevent clogging of the line.

In accordance with a major concept of the invention, as explained hereinbefore, the preconditioned and syrup-impregnated screenings are then discharged into the flash drying stage E, that is to say, into an enlarged confined area in which, while in dispersed or unagglomerated condition, the screenings are contacted with high temperature gases moving at relatively high velocity. In these circumstances the individual particles are conveyed through a zone in which they are contacted, over their entire area, by hot ases. As a result of such hot gas drying while the particles are in dispersed or extenuated condition, the moisture content is rapidly abstracted. As shown, the screenings are discharged from the rotary feeder. into the flash drier 60, to which drier is fed a gaseous drying medium from the inlet line 65.

Preferably the drying medium is comprised of hot flue gases. Where the furnace section of the plant is operated with gas as the fuel, such flue gases may be withdrawn directly'from the furnace itself. In other circumstances, or, in any circumstances if so desired, such flue gases may be withdrawn from the main furnace of the plant and passed through the inlet 62 to the flue gas heater 63. This heater may be provided with suitable heating means, such as the gas burners 84. The flash drier, it will benoted, is provided with the pyrometer 65, which is connected to the temperature controller-recorder 68. This instrument may be associated with the gas burners 64 or with an air damper in a manner known to those'skilled in the art, so as accurately to control the temperature of the gases entering the drier at any desired value.

The flue gases. as shown, enter the flash drier 60 at the upper section thereof and preferably tangentially. The impregnated screenings passing down the central zone of the drier are thus dispersed and given cyclonic motion. The hot flue gases with the dispersed solids then pass through the flash drier discharge I0 and are picked up by the flash drier fan 1|, driven by any suitable mechanism. The gases with their through the line'TZ and are injected tangentially into the upper portion of the flash drier cyclone 13. In the enlarged flashdrier cyclone the large solids gravitate towards the bottom and the suspended solids are thus forced upwardly w gases are withdrawn from the upper section of or;

special precautions must be observedin the con-' re struction of the flashdrier. As a result of considerable experimentation it has been found that. in the flash drying of combustible material such as the screenings here treated, it is important that the discharge elbow 10 be as free as possible matter of actual experience that a typical elbow joint, i. e., one made up of a series of angularly disposed pipe sections, is a distinct fire hazard. With such an angular construction it appears that the hot solids tend to accumulate in the angles and, after an appreciable mass has accu mulated, it spontaneously ignites. This difficulty is completely avoided byadopting the construction shown, that is, to connect the flash drier to the intake of fan 1| through the medium of a substantially straight pipe section 10 which is set at an angle which is less than the critical angle of repose of the solids.

As will particularly be observed, the bottom of the cyclone i3 is somewhat enlarged as at i5. Connected to this section of the cyclone is the blower 16 which is provided with an air inlet line H. During operation this blower picks up the dried solids accumulating in the bottom of the cyclone, immediately and intimately mixes these with cooler'air, admitted through the'air intake 16, and forces them through the discharge line 11 toward the bagging stage F. As will be seen more fully hereinafter, these dried solids reach the bottom of the cyclone at a quite elevated temperature and, in order to prevent too drastic drying or charring, not to say actual combustion. it is necessary that such solids be quickly cooled well below the temperature attained in the drier. This quick or flash cooling is effected to a considerable degree by the blower 15 in that, in

the manner explained, it induces a rapid flow of cooler air and intimatelymixes this with the solids. To positively insure against thermal decomposition of the product, the supply of air to the air inlet 16 may be refrigerated or, as shown, a supplemental blower 1!, having the air inlet I9, may be interposed in the discharge line 11.

40 Preferably this is disposed in rather close proximity to the blower llso as to insure a steep.

temperature gradient for the solids. Blower 18 thus serves as, so tospeak, a booster blower and functions rapidly to force the dried solids to the bagging equipment and also serves as a supplemental cooling means to positively insure a rapid abstraction and dissipation of heat from the solids.

As intimated hereinbefore, theflash drying of distillers spent grains must be carried out under special conditions in order to insure against charring and combustion. It has been found. in actual operations, that in some instances, even whenblower I! was operating, that combustion of the solids occurred. It was determined that this was due to the retention of a the hot gases'in the base of the cyclone which overheated the solids before they could be withdrawn. Slum: these solids have an appreciable specific heat, contact with hot gases for any appreciable length of time would tend to cause combustion. After considerable experimentation it was discovered that such a contingency could positively be avoid- 5 ed by withdrawing a portion of the gases from the than the quantity discharged through the line lower area of the cyclone and preferably from a point relatively closely adjacent the solids dlscharge duct.- The amount so withdrawn need i not be great and, in any event, considerably less 14., The withdrawal of amodicu'm of these hot gases from the acne where the hot solids tend to accumulate appears to reduce the temperature below the critical or danger point.

Such a beneficial result may be secured by the mouth intake for the hot gases.

'fact that excessive drying causes method shown on the drawing. As there shown, a discharge pipe is in communication with the interior of the cyclone I3 and near its lower end. Such pipe terminates in an inverted cone Bl which, at the one time, provides a deflecting battle over which the descending solids pass, and a bell The other end of the line Ill may be connected to a suitable source of suction so as to insure a positive flow of gases from the base of the cyclone. In order to conserve the heat of these gases and thereby insure thermal economies in the operation, the discharge end of the duct 80 preferably is connected to the flue gas heater in the manner shown. In these circumstances the aspirating effect of the gases passing up through the heater 63 induces a flow of hot exhaust gases through the line 80 and thus, to a commensurate extent, cools down the solids. With this type of struc- -ture, it has been found that the fire hazard hereinbefore mentioned is completely avoided.

' The process which is carried out in the described apparatus must be controlled carefully to assure the best results. As noted, the operation effected in preconditioning stage B is primarily for the purpose of insuring optimum penetrability and absorption of the syrup or concentrate from stage C. If insufllcient-water is removed from the solids in this stage, they will absorb considerably less of the syrup than is desirable, due to the fact that such wetted solids are near their point of liquid saturation. Again, if the solids passing to the mingler are too wet, a good portion of the syrup which is picked up in the mingler will appear as a viscous coating around the particles. If, on-the other hand, the solids are subjected to maximum drying in stage B, the relatively viscous syrup, from the concentration stage C, does not actually penetrate the solids but forms a coating on the surface, which coating is partially decomposed Jin passing through the flash drier.

It would seem that the drier the particles which were fed to the mingler, the more rapid and complete would be the penetration by the syrup. This, however, is not the case, due in part to the the hull, fibers to contract or shrink and thereby reduce the porosity and penetrability, and in part to the fact that the interfacial tension between the dried particle and the syrup is much greater than that between a wetted particle and the syrup. The process must, therefore, be so conducted as to attain the optimum between the low potential penetrability of a dried particle, on the one hand, and the low quantitative absorption of a partially saturated particle, on the other. It has been found as a result of considerable experimentation that the optimum preconditioning. i. e., the control of the moisturecontent of the solids discharged from stage B to stage D, lies between approximately 15% andy25% of moisture. Inthis range, optimum wettability and penetration, coupled with optimum homogeneous absorp tion of the syrup in the fibers, is secured.

similarly, to secure the full advantages of the invention, the characteristics of the syrup should be controlled within certain optimum limits. The concentration elected in stage C is therefore carand such a concentrated syrup largely coats the fibers particles which, in the manner explained, tends to decompose in passage through the flash drier.

As a result of numerous tests, it hasbeen found that the optimum concentration of the syrup, for the purposes of the invention, lies in the range of from approximately 20% to 25% of solids. With such a correlation established, namely, the wetting of hot distillers spent grains having a moisture content of from 15 to 25%, with a syrup containing approximately 20, to 25% solids, the syrup rapidly wets and penetrates into the intersticial spaces of the grains, that is to say, the protein syrup is substantially uniformly or homogeneously distributed throughout the body of the particles of spent grains, rather than occurring as a heterogeneous outer surface coating. It will be observed at this point that, if desired, surface tension reducing agents may be added to the solution in tank 34, or at any other appropriate point in the circuit, to increase the speed and degree of penetration.

With such a controlled preconditioning treat-.

ment of the spent grains and the described regulated concentration of the thin slop, coupled with a flash drying and flash cooling of the impregnated grains, a novel improved product is produced. Such a product contains from substantially 28% to 35%, or more, of protein material of which substantially is available. The new product is of a very light brown color and of a characteristic light and ,flufiy texture as com- .pared to the older types of products which are of a darker brown color and of a more gummy texture. I

In order fully to explain the invention to those skilled in the art, a typical operation will be described. It is to be understood that this is an illustrative run and is not intended to restrictively define the permissive manipulative variations which are comprehended within the broader concepts of the invention.

In the operation of the improved method, in the type of apparatus illustrated, the beer still residues are continuously pumped through line I and discharged into the screening section A. The screened and pressed grains,-which at this point contain about 70% of moisture, are passed to the rotary drier I: at the entrance of which they are intimately contacted with hot flash drier exhaust gases flowing through line l3. The exhaust gases entering the drier l2, which are about half saturated with moisture, preferably are maintained at a temperature of approximately 375 F. The spent grains and hot gases pass together through the rotary and are picked up by the fan 40. The speed of flow or retention period in the rotary l2 may be controlled by the fan 40 so that the gases leave the drier at a temperature of approximately 250 F. In the illustrative structure in which the drier I2 is approximately 26 feet long and 6 feet in diameter, this is accomplished by operating thefan 40 at an approximate speed of 1,000 R. P. M. The hot spent grains are then forced upwardly through the line 4| to the cyclone 42. Under these conditions of operation the spent grains are discharged to the hopper 44 with a moisture content within the optimum range, that is to say, between about 15% and 25% of moisture.

- In the hopper 44, or its equivalent, the preconditioned spent grains are contacted with a spray of hot protein syrup of a concentration of between substantially 20% and 25% of solids. The quantity of the concentrate sprayed upon and mingled with the preconditioned grains is so controlled as to increase the moisture content of the preconditioned grains back to approximately 75%, in

saturated and impregnated spent grains are contacted with a high velocity stream of hot gases. In the present operation, as explained, the temperatures of the gases entering the drier are carefully controlled. It has been found as a result of considerable experimentation that the temperature of inlet gases should not exceed 500 F. and preferably should be maintained at about 475 F. The spent grains passing downwardly through the flash drier 65 are therefore contacted for a brief period with a high velocity stream of hot gases. The gaseous suspension of the solids is then picked up by the fan H and forced to the cyclone I3. In ordinary circumstances it will be found that the temperature of the mass passing through the duct 12 is of the order of 375 F. The velocity of the mass through the flash drier should preferably be controlled such that the temperature in the discharge duct 12 should not exceed 425" F. The fluid suspension then passes to the enlarged cyclone 13 in which the velocity is diminished and in which, due to the continual contact with the hot gases, additional amounts of moisture are evaporated from the solids. The dried solids are then picked up by fan It, are'intimately intermixed with cooler air drawn in through inlet 13 and are discharged through duct 11. Booster blower 18 picks up the product, cools it further, and forces it through the discharge line 11 to the cyclone 90, from the upper vent 9| of The dried solids, which at this point are at a temperature of about F. and a moisture content of from approximately 6 to 12%, pass down to cyclone 90 and are discharged to the receiving hopper 92, or to any other convenient storage. From the hopper 92 the material may be directly discharged through the weighing mechanism 93 into bags or other receptacles for shipment.

The hot gases which separate from the dried solids in cyclone 13 pass outwardly through line 14 to, the gas inlet l3 which is connected to the intake of the drier. As noted above, the temperature of the gases passing through this line is maintained at approximately 375 F. In order to accentuate the cooling of the solids in the lower portion of the cyclone, a fraction of the hot gases is continuously withdrawn through line 80 and are recycled through the gascircuit. I

In the type of operation described, and in a plant capable of handling the slope from a 10,000 gallon alcohol unit, approximately'30 tons per day sirable moisture content of the preconditioned solids and the finally dried solids may be secured by controlling the temperature in the several sections of the circuit at the approximate values mentioned and by passing the solids through the flash drier andflash drier cyclone at a speed of approximately 100 feet per second, with an elapsed time through the flash drier and the flash drier cyclone of from about 20 to 30 seconds. In other words, the beneficial results of the invention may be securedby contacting a rapidly flowing stream of the preconditioned solids for a period of from about 20 to.30 seconds with a gaseous medium maintained at a-temperature oi the order of 475 F. and then very, quickly reducing the temperature of the solids down to the order of 100 F. In these circumstances. the beer slops, containing about 7% total solids, are converted to a light, dried feed containing from approximately 6 to 12% of moisture and which feed analyzes from approximately 28% to 35%, or more, of proteins. a

This material co'nstitutesan excellent food of high dietetic value. It will be understood that this particular product, in view of the intimate or homogeneous distribution of the protein content, constitutes an excellent starting material for the production of protein plastics in that it not only contains a high percentage of reactive protein but also contains an excellent ultimate filler, namely, the cellulosic huliflbers of the original grains.

While a preferred method'of procedure has been described herein, it is to be understood that this is given as a typicaland illustrative embodiment of. the underlying principles and not as the only method in which these principles may be eflectuated.

Iclaim:

1. A method of treating distillery slop which comprises, separating the solids or the slop from the solution; concentrating the solids to a moisture content of from approximately 15 to 25%:

' concentrating the solution to a solids content of from substantially 20% to substantially 25%. mixing the concentrate with the solids, and dryin: the mixture. i

2. A method of treating distillery slop which comprises, separating the solids from the solution, passing the separated solids to a dryinl stage and reducing the moisture content oi the solids to between substantially 15 per cent. to substantially 25 per cent.; passing the separated solution to a concentration stage and concentrating the solution therein to a solidscontent 01' between substantially 20. per cent and 25 per cent: absorbing the concentrated solution in the solids and dryingthe resultingmoterialinsflsshdrier to a moisture content of between approximately 6 per cent. and 12 per cent.

3. A method or treating distillery slop which comprises, separating the solids from thesolution, passing the separated solids to a rotary drierand reducing the moisture content oi the solids to between approximately 15 per cent. and

25 per cent.; passing the separated solution to s concentration stage and concentrating the solution therein to a concentration of from substantially 20 per cent. to substantially 25 per cent. of solidspwetting the solids with such solution and drying the resulting material in a flash drier.

4. A method of treating distillery slopwhich "comprises. separating; the insoluble from the solublo material of the slop. drying the separated insoluble material to a moisture content oi i'rom substantially 15 per cent. to substantially 25 per cent.; passing the separated solution to a concentration stage and concentrating such solution to a concentration of from substantially 20 per cent. to substantially 25 percent. of solids; saturating the solids with a suflicient quantity or the solution to raise the moisture content of the solids up to approximately 75 per cent., and drying the product.

5. A method of treating distillery slop which comprises, separating the insoluble from the soluble material of the slo'p,drying the separated insoluble material to a moisture content of irom substantially 15 per cent. to 25 per cent.; passing the separated solution to a concentration stage and concentrating the solution therein to a concentration of from substantially 20 per cent. to substantially 25'per cent. of solids; saturating the solids with a suflicient quantity oi! the concentrated solution to raise the moisture content of such solids up to approximately 75 per cent., and then contacting the saturated material with hot gases for a period of time suillcient to dry the saturated solids, and separating and recovering the dried solids.

6. A method of treating distillery slop which comprises, separating the insoluble from the soluble material of the slop, drying the separated insoluble material to a moisture content or from substantially per cent. to substantially 25 per cent.; passing the separated solution to a concentration stage and concentrating the solution to a concentration of, from substantially per cent. to substantially per cent. of solids saturating the solids with a suii'lcient quantity or the concentrated solution to raise the moisture content of the solids up to approximately 75 per cent., and then contacting the saturated material with hot gases maintained at a temperature between approiimately 500 1"..and 375 1". for a period.

or time summons to dry the saturated solids, and then separating andrecoveringthe dried solids.

7. A method of treating distillery slop. which comprises, screening the slop to recover wet solid screenlngsand a solution; passing the solution -to a concentration stage and there concentrating the solution to a concentration'ot from approximately 20 per cent. to approximately 25 per cent. oisolids; passingthewetsoreeningsthrougha drying reducing the moisture content or the solids to irom substantially 15 per cent. to suhstanflally fi per cent.; saturating the dried solids with the concentrated solution,con-

. tacting the resulting materialtor a brief period or time withhigh temperstiue sal s. s pa atin thegasesfromthresolldsondreooveringthedried tacting them for a brief period of time with hot gases maintained. stempersture oi between substantially 500' land 8'15 1'.

9. A method of treating distillery slop which comprises, passing the slop to a screening stale and there separating solid material from thesolution; passing the screenings to a rotary drier tionsndthendryingth'e'saturstedsolidsbycon-s' gases to dry the screenings to a predeterminedv moisture content between substantially per cent and 25 per cent; passing the gas with the screenings suspended therein to a separating zone and separating the gases from the solids; passing the solution separated out in the screening stage to an evaporator stage and concentrating the solution therein to a predetermined degree between substantially per cent to per cent of solids; commingling the said separated dry solids with the concentrate and passing .the product to a flash drying stage; drying the solids in said drying stage by contact with hot gases, separating the hot gases from the solids and recycling such gases to the rotary drier, and separately withdrawing the dried solids from the flash drying stage. n

10. A method of treating distillery slop which comprises, passing the slop to a screening stage and there separating solid material from the solution; passing the screenings to a rotary drier and there contacting them with hot gases which are substantially saturated with moisture and which gases are maintained at a temperature of substantially 375 F. to thereby reduce the moisture content of the screenings to between 15 per cent and 25 per cent; passing the gases, with the screening suspended therein, to a separating zone and there separating the gases'from the solids; passing the solution separated out in the screening stage to an evaporator stage and concentrating the solution therein to a concentration of substantialy 20% to substantially 25% of solids; co-mingling the said separated solids with the concentrate; passing the co-mingled product to a flash drying stage and contacting the material in such stage for a period of from substantially 20 to substantially 30 seconds with hot gases maintained at a temperature of from substantially 375 F. to 500 F. withdrawing the product, in gaseous suspension, from the flash drying stage and rapidly cooling the product down to a temperature of the order of F.

11. As an article ofcommerce, dried distillers spent grains comprising deamylized grain containing impregnated soluble proteins consisting of the solids of a protein solution of from 20 to 25 per cent protein concentration.

LEO M. CHRISTENSEN. 

